top most important electrical engineering mcq's
TRANSCRIPT
Top Most Important Electrical Engineering
MCQ’s
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1. Electron-hole pair are created by
a. recombination
b. thermal energy
c. Ionization
d. Doping
Ans .b. thermal energy
2. Recombination occurred when
(a) an electron falls into a hole
(b) a positive and a negative ion bond together
(c) a valence electron becomes a conduction electron
(d) a crystal is formed
Ans. (a) an electron falls into a hole
3. Each atom in a silicon crystal has
(a) four valence electrons
(b) four conduction electrons
(c) eight valence electrons, four of its own and four shared
(d)no valence electrons because all are shared with other atoms
Ans. (c) eight valence electrons, four of its own and four shared
4. The process of adding an impurity to an intrinsic
semiconductor is called
(a) doping
(b) recombination
(c)atomic modification
(d)Ionization
Ans. (A) doping
5. The current in a semiconductor is produced by
(a) electrons only
(b) holes only
(c) negative ions
(d)both electrons and holes
Ans. (d)both electrons and holes
6. A trivalent impurity is added to silicon to create
(a) germanium
(b) a p-type semiconductor
(c) an n-type semiconductor
(d) a depletion region
Ans. a p-type semiconductor
7. The purpose of pentavalent impurity is to
(a) reduce the conductivity
(b) increase the number of holes
(c) increase the number of free electrons
(d)create minority carriers
Ans. (c) increase the number of free electrons
8. For a silicon diode, the value of the forward-bias voltage
typically
(a) must be greater than 0.3V
(b) must be greater than 0.7V
(c) depends on the width of depletion region
(d)depends on the concentration of majority carriers
Ans. (b) must be greater than 0.7V
9. When forward biased , a diode
(a) blocks current
(b) conducts current
(c) has a high resistance
(d) drops a large voltage
Ans. B. conducts current
10. The term bias means
(a) the ration of majority carriers to minority carriers
(b) the amount of current across a diode
(c) a dc voltage is applied to control the operation of a device
(d) none of the above
Ans. (c) a dc voltage is applied to control the operation of a
device
11. When a voltmeter is placed across a forward-biased diode, it
will read a voltage approximately equal to
(a) the bias battery voltage
(b) 0V
(c) the diode barrier potential
(d) the total circuit voltage
Ans. (c) the diode barrier potential
12. In a LED, the light is produced by a solid state process called as
(a) light radiation
(b) electroluminescence
(c) light multiplication
(d) Phosphoresce
Ans. (b) electroluminescence
13. Efficiency of LED is given by
(a) light to light conversion
(b) light to electrical conversion
(c) electrical power to visible light conversion
(d) none of above
Ans. (c) electrical power to visible light conversion
14. The wavelength of the light emitted and its colour depends on
the
(a) forward voltage
(b) forward current
(c) band gap energy of the material forming P-N junction
(d) none of the above
Ans. (c) band gap energy of the material forming P-N junction
15. Although current is blocked in reverse bias,
(a) there is some current due to majority carrier
(b) there is very small current due to minority carriers
(c) there is an avalanche current
(d) none of the above
Ans. (b) there is very small current due to minority carriers
16. The cathode of zener diode in a voltage regulator is normally
(a) more positive than the anode
(b) more negative than the anode
(c) at +0.7 V
(d) grounded
Ans.(a) more positive than the anode
17. If a certain zener diode has a zener voltage of 3.6V,it
operates in
(a) regulated breakdown
(b) Zener breakdown
(c) forward conduction
(d) avalanche breakdown
Ans. (b) Zener breakdown
18. When operated in cut-off and saturation, the transistor acts
like
(a) linear amplifier
(b) a switch
(c) a variable capacitor
(d) a variable resistance
Ans. (b) Switch
19. The JFET is
(a) a unipolar device
(b) a voltage-controlled device
(c) a current controlled device
(d) the supply voltage is too high
Ans. (a) a unipolar device
20. The channel of JFET is between the
(a) gate and drain
(b) drain and source
(c) gate and source
(d) input and output
Ans. (b) drain and source
21. A JFET always operates with
(a) gate to source pn junction reverse-biased
(b) gate to source pn junction forward-biased
(c) the drain connected to ground
(d) the gate connected to source
Ans. (a) gate to source pn junction reverse-biased
22. IDSS is
(a) the drain current with the source shorted
(b) the drain current at cutoff
(c) the maximum possible drain current
(d) the midpoint drain current
Ans. (c) the maximum possible drain current
23. Drain current in the constant-current area increases when
(a) the gate-to-source bias voltage decreases
(b) the gate-to-source bias voltage increases
(c) the drain to source voltage increases
(d) the drain to source voltage decreases
Ans. (a) the gate-to-source bias voltage decreases
24. At cutoff, the JFET channel is
(a) at its widest point
(b) completely closed by the depletion region
(c) extremely narrow
(d) reverse-biased
Ans. (b) completely closed by the depletion region
25. A thyristor has
(a) 2 pn junctions
(b) 3 pn junctions
(c) 4 pn junctions
(d) only 2 terminals
Ans. (b) 3 pn junctions
26. Common types of thyristors include
(a) BJTs and SCRs
(b) UJTs and PUTs
(c)FETs and TRIACs
(d)DIACs and TRIACs
Ans. (d)DIACs and TRIACs
27. The diac is
(a) a thyristor
(b) a bilateral, two terminal device
(c) like two parallel 4-layer diodes in reverse directions
(d)all of these
Ans. (d)all of these
28. The triac is
(a) like a bidirectional SCR
(b) a four-terminal device
(c) not a thyristor
(d) answers (a) and (b)
Ans. (a) like a bidirectional SCR
29. The value of reverse bias resistance for an ideal diode is
__________
(a) infinity
(b) 0
(c) 1
(d) none of the above
Ans. (a) infinity
30. Semiconductor material have __________ temp. coefficient
(a) Positive
(b) Negative
(c) Both positive and negative
(d) None
Ans. (b) Negative
31. A zener diode works on the principal of
(a) tunneling of charge carriers across junction
(b) thermionic emission
(c) diffusion of charge carriers across junction
(d) hopping of charge carriers across junction
Ans. (c) diffusion of charge carriers across junction
32. Optical fiber cable carries following
(a) Electrical signal
(b) Light signal
(c) Sound signal
(d) None of above
Ans. (b) Light signal
